Conventional magnetic recording heads can be fabricated in a number of ways. FIG. 1 is a flow chart depicting a conventional method 10 for fabricating an interferometric tapered waveguide (I-TWG) in an energy assisted magnetic recording (EAMR) transducer using a conventional process. An I-TWG waveguide includes a y-splitter or a multimode interferometric (MMI) device which splits the waveguide into two arms. A path difference may be introduced between the two arms. The I-TWG may be used to provide energy having the desired phase difference to a near-field transducer (NFT). The method 10 may thus be used to provide fabricate I-TWG that provides laser energy to the NFT of an EAMR transducer. For simplicity, some steps are omitted in the method 10.
The bottom cladding, core, and top cladding layers are deposited, via step 12. The bottom and top cladding are typically formed of silicon dioxide. The core is typically formed of Ta2O5. A trench is formed in the top cladding and core layers, via step 14. Because the core layer is overetched, the trench is typically also formed into a portion of the bottom cladding layer. The trench removes the core and top cladding layers between the arms of the waveguide. Thus, the arms of the I-TWB waveguide are defined in step 14.
A single conventional dielectric layer is deposited to fill the trench, via step 16. For example, the dielectric layer deposited may be two hundred fifty nanometers or more thick. The dielectric layer is typically silicon dioxide. Fabrication of the conventional EAMR transducer may then be completed.
FIGS. 2-3 depict plan and side views, respectively, of the conventional EAMR transducer 50. The EAMR transducer includes a waveguide 60. The conventional waveguide is a conventional I-TWG 60. The conventional I-TWG 60 includes a bottom cladding layer 61, arms 62 and 64 formed from the core layer and a top cladding layer 66. In forming the I-TWG 60, a trench 52 is formed in the top cladding and core layers, which is refilled with a dielectric 68. The top cladding 66, dielectric 68 and bottom cladding 61 layers may be formed of the same material. Thus, the boundaries between the layers 61, 66 and 28 are denoted by dashed lines.
Although the conventional method 10 can be used to form the conventional I-TWG 60, there are drawbacks. Some portions of the trench 52 are close to the split between the arms 62 and 64. In this region, refilling of the trench 52 through the deposition of the dielectric layer 68 in step 16 may result in voids 70. The void 70 is an empty space surrounded by the dielectric layer 68. The geometry of the void 70 may be difficult to control. The presence of the void 70 may alter the optical properties of the conventional I-TWG 60. For example, the phase difference between light traversing the arm 62 and the arm 64 may be changed. Further, there may be additional losses due to scattering of light from the void 70. Thus, performance and efficiency of the conventional I-TWG 60 may be adversely affected.
Accordingly, what is needed is an improved method for fabricating an I-TWG waveguide in an EAMR transducer.